A power steering mechanism usually has a surplus of power steering fluid contained in a reservoir. A filter is usually provided to clean the fluid as it circulates through the reservoir and back to the power steering mechanism. Known reservoirs generally comprise a well to contain the fluid, an inlet pipe to receive the fluid from the power steering mechanism, an outlet pipe to permit the fluid to flow back into the power steering mechanism, a filter positioned over the inlet pipe to filter impurities from the power steering fluid as it passes into the well, and a removable well cap to permit an operator to add additional power steering fluid or to change the filter. The filter commonly used is a ring-type filter which surrounds the inlet so that incoming power steering fluid flows into the centre of the ring, through the filter medium from an inside surface to an outside surface of a filter medium and into the well. The centre orifice of the ring filter is located over the inlet and is topped with a pressure relief valve to permit fluid under excessive pressure to flow directly through the centre orifice of the ring through the pressure relief valve and into the well without passing through the filter. A dipstick is ordinarily provided in a port in the removable cap to test the level of the fluid in the well without removal of the well cap. Usually the fluid level in the well completely submerses the filter.